1. Field of the Invention
The present invention relates generally to microphones, and more particularly to an MEMS (micro electromechanical system) microphone and method for manufacturing the same.
2. Description of Related Art
Sound is one important means by which people communicate with each other, thus creating new methods for sound transference which allows greater communication between people is an important area of technological development. Electroacoustic transducers are key components in transferring sound. Microphone is a typical electroacoustic transducer. There are many different types of microphones, such as ECM (electric condenser microphone), or MEMS (micro electromechanical system) microphone.
An MEMS microphone includes a casing, a microphone chip arranged in the casing, and circuits (not shown) disposed in the casing and electrically connected with the microphone chip. The microphone chip includes an oscillating diaphragm, a silicon back plate, an isolation layer and a silicon substrate. The back plate defines a plurality of holes therethrough. An air interstice is formed between the oscillating diaphragm and the back plate. The back plate, the isolation layer and the oscillating diaphragm are placed on the silicon substrate in that order. The silicon substrate provides a rear acoustic chamber therein. The acoustic chamber communicates with the oscillating diaphragm via the holes of the back plate so that when the oscillating diaphragm is driven to vibrate by a sound source, an electrical signal is generated.
In the MEMS microphone, the acoustic chamber should preferrably be designed to have a large size so as to increase the sensitivity of the MEMS microphone. However, since the acoustic chamber of the conventional MEMS microphone is formed by etching the silicon substrate, to form a large acoustic chamber in the conventional MEMS microphone will increase the size of the MEMS microphone, which violates the compact size and lightness requirements for the MEMS microphone. Furthermore, to etch the large acoustic chamber in the silicon substrate is time consuming and costly. Therefore, it is necessary to provide an inexpensive MEMS microphone having a large acoustic chamber with a size compatible with modern portable technologies.